1. Field of the Invention
This invention relates to a nonlinearity-caused distortion compensating system which can be used in, for example, a radio transmitter having a modulator and an RF amplifier. In general, xe2x80x9cnonlinearity-caused distortionxe2x80x9d is shortened to xe2x80x9cnonlinear distortionxe2x80x9d.
2. Description of the Related Art
Japanese published unexamined patent application 4-290321 discloses a nonlinearity-caused distortion compensating system (a nonlinear distortion compensating system) used in a radio transmitter having a modulator and an RF amplifier. In Japanese application 4-290321, a digital filter processes a digital baseband signal into a processing-resultant digital signal, and a digital-to-analog converter following the digital filter changes the processing-resultant digital signal into a corresponding analog baseband signal.
In addition, a modulator following the digital-to-analog converter subjects the analog baseband signal to a modulation process, thereby converting the analog baseband signal into a modulation-resultant signal. Furthermore, a first frequency converter following the modulator changes the modulation-resultant signal into a corresponding RF signal. Then, an RF power amplifier following the first frequency converter amplifies the RF signal.
Generally, the input-output characteristic of an RF power amplifier has a nonlinearity which distorts the output signal of the RF power amplifier.
In Japanese application 4-290321, a nonlinearity-caused distortion in the output signal of the RF power amplifier is previously determined. The digital filter includes a ROM storing signals which represent corrective coefficients predetermined to compensate for a nonlinearity-caused distortion in the output signal of the RF power amplifier.
In Japanese application 4-290321, the RF power amplifier is followed by a second frequency converter which changes the output signal of the RF power amplifier into a corresponding IF signal. A demodulator following the second frequency converter subjects the IF signal to a demodulation process, thereby converting the IF signal into a corresponding demodulation-resultant signal. The demodulator extracts a polarity signal and an error signal from the demodulation-resultant signal. A correlator following the demodulator detects a correlation between the polarity signal and the error signal, and outputs a signal representing the detected correlation. An integrator following the correlator integrates the output signal of the correlator into a control signal. The integrator outputs the control signal to the digital filter.
In Japanese application 4-290321, at an initial stage of operation of the transmitter, the digital filter processes the digital baseband signal in response to the corrective coefficients and the control signal so that a nonlinearity-caused distortion in the output signal of the RF power amplifier can be compensated for. During a normal stage of operation of the transmitter which succeeds the initial stage thereof, the digital filter processes the digital baseband signal in response to the control signal only.
Japanese application 4-290321 considers a nonlinearity-caused distortion in the output signal of the RF power amplifier. Generally, the input-output characteristic of a modulator also has a nonlinearity which distorts the output signal of the modulator.
Japanese application 4-290321 fails to consider a nonlinearity-caused distortion in the output signal of the modulator.
It is an object of this invention to provide a system which can compensate for a signal distortion caused by a nonlinearity of a modulator.
A first aspect of this invention provides a nonlinearity-caused distortion compensating system (a nonlinear distortion compensating system) in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; and third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion.
A second aspect of this invention is based on the first aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing a relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing a relation between the second distortion compensating coefficients and the value calculated by the power calculating portion.
A third aspect of this invention is based on the first aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations.
A fourth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means.
A fifth aspect of this invention is based on the fourth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing a relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion.
A sixth aspect of this invention is based on the fourth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations.
A seventh aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to equations, the third compensation coefficients being designed to compensate for a variation in characteristics of at least one of the quadrature modulating portion and the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, and the third compensation coefficients calculated by the calculator; a compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier and to compensate for a variation in the characteristics of at least one of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, and for updating the equations used by the calculator in response to the calculated error.
An eighth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the compensation coefficients determined by the first means to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; second means for feeding the second baseband signals generated by the compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; third means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, and for updating, in response to the calculated error, the relation between the compensation coefficients and the value calculated by the power calculating portion which is provided by the first means.
A ninth aspect of this invention is based on the eighth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the compensation coefficients and the value calculated by the power calculating portion, and the third means includes a second memory for storing signals representing a second reference table providing a relation between the corrective coefficients and the value calculated by the power calculating portion.
A tenth aspect of this invention is based on the eighth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the compensation coefficients from the value calculated by the power calculating portion according to first equations, and the third means includes a second calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to second equations.
An eleventh aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion, the first compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a calculator for calculating second compensation coefficients from the value calculated by the power calculating portion according to equations, the second compensation coefficients being designed to compensate for a variation in characteristics of at least one of the quadrature modulating portion and the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means and the second compensation coefficients determined by the calculator; a compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier and to compensate for a variation in the characteristics of at least one of the quadrature modulating portion and the RF power amplifier; second means for feeding the second baseband signals generated by the compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; third means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, and for updating the equations used by the calculator in response to the calculated error.
A twelfth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the fourth means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means.
A thirteenth aspect of this invention is based on the twelfth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing a relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion, and the fourth means includes a third memory for storing signals representing a third reference table providing a relation between the corrective coefficients and the value calculated by the power calculating portion.
A fourteenth aspect of this invention is based on the twelfth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations, and the fourth means includes a third calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to third equations.
A fifteenth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to equations, the third compensation coefficients being designed to compensate for a variation in characteristics of at least one of the quadrature modulating portion and the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, and the third compensation coefficients calculated by the calculator; a compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier and to compensate for a variation in the characteristics of at least one of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the compensating portion to the quadrature modulating portion; a signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a quadrature demodulator for demodulating the signal portion separated by the signal divider into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the fourth means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, and for updating the equations used by the calculator in response to the calculated error.
A sixteenth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, for updating, in response to the calculated error, the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the signal portion separated by the first signal divider, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means when the switch selects the signal portion separated by the second signal divider.
A seventeenth aspect of this invention is based on the sixteenth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion.
An eighteenth aspect of this invention is based on the sixteenth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations.
A nineteenth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a first calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to first equations, the third compensation coefficients being designed to compensate for a variation in characteristics of the quadrature modulating portion; a second calculator for calculating fourth compensation coefficients from the value calculated by the power calculating portion according to second equations, the fourth compensation coefficients being designed to compensate for a variation in characteristics of the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, the third compensation coefficients calculated by the first calculator, and the fourth compensation coefficients calculated by the second calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for variations in the characteristics of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the signal portion separated by the first signal divider, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the signal portion separated by the second signal divider.
A twentieth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating, in response to the calculated error, the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the signal portion separated by the first signal divider, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means when the switch selects the signal portion separated by the second signal divider.
A twenty-first aspect of this invention is based on the twentieth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion, and the fourth means includes a third memory for storing signals representing a third reference table providing a relation between the corrective coefficients and the value calculated by the power calculating portion.
A twenty-second aspect of this invention is based on the twentieth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations, and the fourth means includes a third calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to third equations.
A twenty-third aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a first calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to first equations, the third compensation coefficients being designed to compensate for a variation in characteristics of the quadrature modulating portion; a second calculator for calculating fourth compensation coefficients from the value calculated by the power calculating portion according to second equations, the fourth compensation coefficients being designed to compensate for a variation in characteristics of the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, the third compensation coefficients calculated by the first calculator, and the fourth compensation coefficients calculated by the second calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for variations in the characteristics of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the signal portion separated by the first signal divider, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the signal portion separated by the second signal divider.
A twenty-seventh aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the compensation coefficients determined by the first means to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; second means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; third means for determining corrective coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating, in response to the calculated error, the relation between the compensation coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the signal portion separated by the second signal divider, and for updating, in response to the calculated error, the relation between the corrective coefficients and the value calculated by the power calculating portion which is used by the third means when the switch selects the signal portion separated by the first signal divider.
A twenty-fifth aspect of this invention is based on the twenty-fourth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the compensation coefficients and the value calculated by the power calculating portion, and the third means includes a second memory for storing signals representing a second reference table providing the corrective coefficients and the value calculated by the power calculating portion.
A twenty-sixth aspect of this invention is based on the twenty-fourth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the compensation coefficients from the value calculated by the power calculating portion according to first equations, and the third means includes a second calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to second equations.
A twenty-seventh aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion, the first compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a first calculator for calculating second compensation coefficients from the value calculated by the power calculating portion according to first equations, the second compensation coefficients being designed to compensate for a variation in characteristics of at least one of the quadrature modulating portion and the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means and the second compensation coefficients determined by the first calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for a variation in the characteristics of at least one of the quadrature modulating portion and the RF power amplifier; second means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a first signal divider connected to the quadrature modulating portion for separating a portion from an output signal of the quadrature modulating portion; a second signal divider connected to the RF power amplifier for separating a portion from an output signal of the RF power amplifier; a switch for selecting one of the signal portion separated by the first signal divider and the signal portion separated by the second signal divider; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; third means for determining first corrective coefficients in response to the value calculated by the power calculating portion, the first corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a second calculator for calculating second corrective coefficients from the value calculated by the power calculating portion according to second equations, the second corrective coefficients being designed to compensate for a variation in characteristics of the quadrature demodulator; a corrective-coefficient calculating portion for calculating final corrective coefficients from the first corrective coefficients determined by the third means and the second corrective coefficients determined by the second calculator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the final corrective coefficients determined by the corrective-coefficient calculating portion to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator, and to compensate for a variation in the characteristics of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the signal portion separated by the second signal divider, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the signal portion separated by the first signal divider.
A twenty-eighth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier following the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, for updating, in response to the calculated error, the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the output signal of the quadrature modulating portion, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means when the switch selects the output signal of the RF power amplifier.
A twenty-ninth aspect of this invention is based on the twenty-eighth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion.
A thirtieth aspect of this invention is based on the twenty-eighth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations.
A thirty-first aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a first calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to first equations, the third compensation coefficients being designed to compensate for a variation in characteristics of the quadrature modulating portion; a second calculator for calculating fourth compensation coefficients from the value calculated by the power calculating portion according to second equations, the fourth compensation coefficients being designed to compensate for a variation in characteristics of the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, the third compensation coefficients calculated by the first calculator, and the fourth compensation coefficients calculated by the second calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for variations in the characteristics of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; and an updating portion for calculating an error between the first baseband signals and the third baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the output signal of the quadrature modulating portion, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the output signal of the RF power amplifier.
A thirty-second aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second distortion compensating coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second distortion compensating coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a compensation-coefficient calculating portion for calculating final distortion compensating coefficients from the first distortion compensating coefficients determined by the first means and the second distortion compensating coefficients determined by the second means; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final distortion compensating coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating, in response to the calculated error, the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the output signal of the quadrature modulating portion, and for updating, in response to the calculated error, the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion which is used by the second means when the switch selects the output signal of the RF power amplifier.
A thirty-third aspect of this invention is based on the thirty-second aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the first distortion compensating coefficients and the value calculated by the power calculating portion, and the second means includes a second memory for storing signals representing a second reference table providing the relation between the second distortion compensating coefficients and the value calculated by the power calculating portion, and the fourth means includes a third memory for storing signals representing a third reference table providing a relation between the corrective coefficients and the value calculated by the power calculating portion.
A thirty-fourth aspect of this invention is based on the thirty-second aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the first distortion compensating coefficients from the value calculated by the power calculating portion according to first equations, and the second means includes a second calculator for calculating the second distortion compensating coefficients from the value calculated by the power calculating portion according to second equations, and the fourth means includes a third calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to third equations.
A thirty-fifth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the first compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature modulating portion; second means for determining second compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the second compensation coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the RF power amplifier; a first calculator for calculating third compensation coefficients from the value calculated by the power calculating portion according to first equations, the third compensation coefficients being designed to compensate for a variation in characteristics of the quadrature modulating portion; a second calculator for calculating fourth compensation coefficients from the value calculated by the power calculating portion according to second equations, the fourth compensation coefficients being designed to compensate for a variation in characteristics of the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means, the second compensation coefficients determined by the second means, the third compensation coefficients calculated by the first calculator, and the fourth compensation coefficients calculated by the second calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for signal distortions caused by the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for variations in the characteristics of the quadrature modulating portion and the RF power amplifier; third means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; fourth means for determining corrective coefficients in response to the value calculated by the power calculating portion, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the output signal of the quadrature modulating portion, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the output signal of the RF power amplifier.
A thirty-sixth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining compensation coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the compensation coefficients determined by the first means to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier; second means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; third means for determining corrective coefficients in response to the value calculated by the power calculating portion according to a relation therebetween, the corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the corrective coefficients determined by the third means to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating, in response to the calculated error, the relation between the compensation coefficients and the value calculated by the power calculating portion which is used by the first means when the switch selects the output signal of the RF power amplifier, and for updating, in response to the calculated error, the relation between the corrective coefficients and the value calculated by the power calculating portion which is used by the third means when the switch selects the output signal of the quadrature modulating portion.
A thirty-seventh aspect of this invention is based on the thirty-sixth aspect thereof, and provide a nonlinearity-caused distortion compensating system wherein the first means includes a first memory for storing signals representing a first reference table providing the relation between the compensation coefficients and the value calculated by the power calculating portion, and the third means includes a second memory for storing signals representing a second reference table providing the corrective coefficients and the value calculated by the power calculating portion.
A thirty-eighth aspect of this invention is based on the thirty-sixth aspect thereof, and provides a nonlinearity-caused distortion compensating system wherein the first means includes a first calculator for calculating the compensation coefficients from the value calculated by the power calculating portion according to first equations, and the third means includes a second calculator for calculating the corrective coefficients from the value calculated by the power calculating portion according to second equations.
A thirty-ninth aspect of this invention provides a nonlinearity-caused distortion compensating system in a radio transmitter having be a quadrature modulating portion and an RF power amplifier. The RF power amplifier follows the quadrature modulating portion. The system comprises a power calculating portion for calculating a value related to a power of a transmission signal from first baseband signals quadrature with respect to each other; first means for determining first compensation coefficients in response to the value calculated by the power calculating portion, the first compensation coefficients being designed to compensate for a signal distortion caused by at least one of a nonlinearity of the quadrature modulating portion and a nonlinearity of the RF power amplifier; a first calculator for calculating second compensation coefficients from the value calculated by the power calculating portion according to first equations, the second compensation coefficients being designed to compensate for a variation in characteristics of at least one of the quadrature modulating portion and the RF power amplifier; a compensation-coefficient calculating portion for calculating final compensation coefficients from the first compensation coefficients determined by the first means and the second compensation coefficients determined by the first calculator; a distortion compensating portion for converting the first baseband signals into second baseband signals quadrature with respect to each other in response to the final compensation coefficients calculated by the compensation-coefficient calculating portion to compensate for a signal distortion caused by at least one of the nonlinearity of the quadrature modulating portion and the nonlinearity of the RF power amplifier, and to compensate for a variation in the characteristics of at least one of the quadrature modulating portion and the RF power amplifier; second means for feeding the second baseband signals generated by the distortion compensating portion to the quadrature modulating portion; a switch connected to the quadrature modulating portion and the RF power amplifier for selecting one of an output signal of the quadrature modulating portion and an output signal of the RF power amplifier; a signal divider connected to the switch for separating a portion from the signal selected by the switch; a quadrature demodulator for demodulating the signal portion selected by the switch into third baseband signals quadrature with respect to each other; third means for determining first corrective coefficients in response to the value calculated by the power calculating portion, the first corrective coefficients being designed to compensate for a signal distortion caused by a nonlinearity of the quadrature demodulator; a second calculator for calculating second corrective coefficients from the value calculated by the power calculating portion according to second equations, the second corrective coefficients being designed to compensate for a variation in characteristics of the quadrature demodulator; a corrective-coefficient calculating portion for calculating final corrective coefficients from the first corrective coefficients determined by the third means and the second corrective coefficients determined by the second calculator; a correcting portion for converting the third baseband signals generated by the quadrature demodulator into fourth baseband signals quadrature with respect to each other in response to the final corrective coefficients determined by the corrective-coefficient calculating portion to compensate for a signal distortion caused by the nonlinearity of the quadrature demodulator, and to compensate for a variation in the characteristics of the quadrature demodulator; and an updating portion for calculating an error between the first baseband signals and the fourth baseband signals, for updating the first equations used by the first calculator in response to the calculated error when the switch selects the output signal of the RF power amplifier, and for updating the second equations used by the second calculator in response to the calculated error when the switch selects the output signal of the quadrature modulating portion.